1. Technical Field
The field of the currently claimed embodiments of this invention relates to ultrasound systems, and more particularly to a synthetic aperture ultrasound system.
2. Discussion of Related Art
Ultrasound imaging is used in various medical diagnoses. Resolution of the ultrasound image depends on the center frequency of transmission and the F-number determined by the imaging depth and the aperture size. Even though higher frequency transmission enables one to achieve higher resolution, high center frequency is easily absorbed in the near field due to strong attenuation, so that the contrast decreases with the increased image depth. Thus, only low frequency and low resolution are available if the region of interest is located in the far field.
Synthetic aperture is a technique to synthetize transmit and receive apertures, and utilizes wider aperture in reconstruction. Synthetic aperture is actively applied to medical ultrasound and successfully contributes to an increase in the image resolution[1-3]. Nevertheless, an ultrasound array has a fixed number of elements, so that the maximum available aperture size depends on the width of the ultrasound transducer and the number of elements on it. Therefore, it is challenging to achieve higher resolution in conventional synthetic aperture imaging since the F number becomes too high in the deeper regions. Although using large arrays is a possible solution, these require huge costs, and the flexibility for different usage requirements is low.